Re: SQL:2023 JSON simplified accessor support

> <v16-0007-Implement-jsonb-wildcard-member-accessor.patch><v16-0001-Allow-transformation-of-only-a-sublist-of-subscr.patch><v16-0004-Extract-coerce_jsonpath_subscript.patch><v16-0006-Implement-Jsonb-subscripting-with-slicing.patch><v16-0005-Implement-read-only-dot-notation-for-jsonb.patch><v16-0003-Export-jsonPathFromParseResult.patch><v16-0002-Allow-Generic-Type-Subscripting-to-Accept-Dot-No.patch>

A few more comment for v16.

1 - 0002
```
--- a/contrib/hstore/hstore_subs.c
+++ b/contrib/hstore/hstore_subs.c

- if (isSlice || list_length(*indirection) != 1)
+ if (ai->is_slice || list_length(*indirection) != 1)
```

We should put list_length() check before ai->is_slace. Because when indirection length is greater than 1, it take a single check; other it may need to check the both conditions.

2 - 0002 - also in hstore_subs.c
```
*indirection = NIL;
```

We should do “list_delete_first_n(indirection, 1)”.

3 - 0003
```
+Datum
+jsonPathFromParseResult(JsonPathParseResult *jsonpath, int estimated_len,
+ struct Node *escontext)
+{
```

`jsonpath` is not changed in this function, so it should be defined as a const: “const JsonPathParseResult *jsonpath”.

4 - 0004
```
+ Oid targets[2] = {INT4OID, TEXTOID};
+
+ /*
+ * Jsonb can handle multiple subscript types, but cases when a
+ * subscript could be coerced to multiple target types must be
+ * avoided, similar to overloaded functions. It could be possibly
+ * extend with jsonpath in the future.
+ */
+ for (int i = 0; i < 2; i++)
```

This is a nit optimization. We can do:

Oid targets[] = {INT4OID, TEXTOID};
For (int I = 0; I < sizeof(targets) / sizeof(targets[0]); I ++)

This way lets the compiler to decide length of “targets”. So that avoids hard code “2” in “for”. If we need to add more elements to “targets”, we can just add it without updating “for”.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/